The Response Of Physical And Chemical Characteristics To Microbial Flora's Construction In Tilapia Aquaculture Ponds

The tilapia(Oreochromis niloticus)industry occupies an important place in the structure of aquaculture in our country and the ponds aquaculture is the main way of tilapia production in China to provide the world with abundant aquatic products and animal protein sources.To keep good pond aquaculture environment is of great significance for the health of tilapia aquaculture,the safety quality of tilapia product and the rapid development of the whole tilapia industry.This paper first was set out from studying the water quality index from tilapia aquaculture ponds,monitoring various kinds of water quality index in the process of the tilapia breeding,analyzing and summarizing the changing rule of water quality factors.Used path analysis method further to explore the influence of the changes of water environmental factors on concentrations of chlorophyll a.Then focus on studying biochemical characteristics of sediment in tilapia aquaculture pond,monitoring and summarizing the change trend of each physical and chemical index,exploring the area pollutants producing coefficient of each nutrient index,comparing phosphorus content and alkaline phosphatase activity of sediment in different regions tilapia aquaculture pond,researching the effect of Cadmium on degradation of Malachite Green in sediment.Finally,studying the structure and its changs of microbial community in sediment through high-throughput sequencing technologies.This research established and improved the detection technology of sediment physical and chemical index based on the tests,preliminary discussed the response of physical and chemical characteristics to microbial flora's construction in tilapia aquaculture ponds.The result of study on the changing rule of water quality factors in tilapia intensive pond showed that the maximum content of total nitrogen was 8.291 mg·L-1 and appeared at week 16,the maximum content of total phosphorus was 2.650 mg L-1 and appeared at week 14.The content of Chl.a increased relatively flat in the first 12 weeks,but increased significantly from week 12 to 18 and the maximum content reached 981.3 mg·m-3.The content of ammonia nitrogen increased to 1.819 mg·L-1 gradually in the first 12 weeks,no big difference in later stage and keep around 1.3 mg·L-1.The content of nitrite nitrogen and nitrate nitrogen were with significant differences in the earlier stage and the later stage respectively.The content of NO3--N was 0.2260 mg·L-1 at week 2 and 0.1060 mg·L-1 at week 4,while the content was very low from the beginning of the sixth week.The content of NO2--N was very low in the first 12 weeks,while it showed certain content until week 14.The time scale cluster analysis and principal component analysis indicated that the water quality indicators could be classified as three sub-system types,so we can divide the breeding process into earlier,middle and later stage.Discriminanted analysis showed that the earlier stage had significant positive correlation with NO3--N,while had negative correlation with Chl.a&NO2--N;the middle stage had positive correlation with TP and had negative correlation with TN&NH4+-N;the later stage had positive correlation with TN.Used the path analysis method to study the influence of the changes of water environmental factors on concentrations of Chl.a.The results of correlation and multiple regression analysis of water quality indicators showed that TN and NO2--N were with little impact to Chl.a.The results of path analysis indicated that the resultant direct path coefficient of pH,TP,NH4+-N and NO3--N were 0.416,0.325,0.404 and-0.223 respectively,whereas the sum of indirect path coefficient were-0.276,0.198,0.072 and-0.163 respectively.The sum of absolute function value about the change of environmental factors impact directly and indirectly on the growth and reproduction of phytoplankton were about 65.9%and 34.1%respectively.The determination coefficient showed TP and NH4+-N had the largest influence on Chl.a concent and the determining value reached 0.235 and 0.221.The established multiple regression equation of the relationship between Chl.a and environmental factors in tilapia aquaculture ponds was Chl.a=-1021.197 + 137.322 ×pH + 151.571 × TP+ 157.374 ×NH4+-N-555.221 ×NO3--N.During the process of tilapia broodstock rearing in ponds,the production of dry mud,organic matter,total nitrogen and total phosphorus of sediment showed a first increas-ed and then decreased trend.The time from July to September was the main production period of each nutrient and the production percentage all closed to 80%of the total.The content of ammonia nitrogen increased gradually,reached a peak in early August,then maintained at the peak level.The content of nitrite nitrogen between all the samples were basically same in earlier aquaculture stage and decreased in middle stage with a big difference,while raised again in later stage.The results of study on pollutants producing coefficient of sediment in tilapia intensive pond showed that the pollutants producing coefficient of dry mud,organic matter,total nitrogen,total phosphorus and available phosphorus in Nanquan tilapia aquiculture ponds were 9.904-47.686 kg·m-2,11.068-17.680 kg·m-2,0.084-0.151 kg·m-2,0.025-0.053 kg·m-2 and 0.070-0.422 g·m-2.The pollutants producing coefficient of dry mud,organic matter,total nitrogen and total phosphorus in Qiting tilapia aquiculture ponds were 11.267-50.558 kg·m-2,6.843-26.223 kg·m-2,0.087-0.309 kg ·m-2and 0.016-0.086 kg·m-2.The results of study on the relationship between total phosphorus content and alkaline phosphatase activity of sediment in tilapia aquaculture ponds in Jiangsu and Yunnan provinces showed that the total phosphorus content and alkaline phosphatase activity of the two sample groups in Jiangsu province's ponds were 0.116%and 0.176%,1329.2 mg ·(kg·24 h)-1 and 1539.1 mg·(kg·24 h)-1,the total phosphorus content and alkaline phosp-hatase activity of the sample in Yunnan province's ponds were 1.22%,2467.7 mg(kg·24 h)-1.The change trend of the three groups' total phosphorus content and phosphatase activity data are consistent,which have significantly positive relation,but have no linear relationship.The results of study on the effect of Cadmium on degradation of Malachite Green in sediment from an aquaculture pond showed that the impact of heavy metal Cd to degradation of MG was very small,and the degradation of MG won't be complicated with the existence of Cd.At the same concentrations,the degradation trend of MG between single pollution and compound pollution were almost unanimous,and the kinetic equations for MG degradation were also similar between them.Under the compound pollution of MG with 0.0 mg· kg-1 Cd,0.5 mg·kg-1 Cd and 5.0 mg·kg-1 Cd,the half-life of high MG concentration(2.5 mg·kg-1)groups were 3.432±0.059,3.362±0.041,and 3.456±0.088 d respectively,and the half-life of low MG concentration(0.25 mg·kg-1)groups were 4.140±0.042,4.318±0.167 and 4.271 ±0.045 d respectively.However,Cd had significant influence on the presence of leuco malachite green(LMG).At high MG concentration,LMG was in order of 0.5 mg·kg-1 Cd>5.0 mg·kg-1 Cd>0 mg·kg-1 Cd treatments during the whole experimental period.The results of study on structure and its changs of microbial community in sediment from aquaculture ponds showed that the average percentage of Proteobacteria,Bacteroides,Acidobacteria,Actinobacteria,Chlorobi,Firmicutes,Fusobacteria,Spirochaetes,Verrucomicrobia microorganisms more than 1%in sediments.Proteobacteria and Bacteroides were the dominant phylums and the average percentage reached 53.5%and 22.2%.Cetobacterium,Dechloromonas and Geobacter were the dominant genus,the average percentage reached 4.9%,11.3%and 5.9%respectively.In the breeding process of tilapia,the average percentage of Desulfobacterales microorganisms decreased gradually from about 6%to 1.5%.The percentage of Fusobacteriia microorganisms showed a trend of first increased and then decreased,the peak was 9.4%and appeared in late August.The content of SB-1 family microorganisms was stable in the no snail growth pond,and increased with the number of snail.The content of Flavobacteriaceae microorganisms decreased gradually from the middle aquaculture stage.The initial average percentage of Nitrospira flora was high,then decreased over time and maintained at 0.5%level in later stage.